Error when deleting or editing case states

I get the following error message when trying to delete or edit a case states (adding a case state is ok);

* warning: array_merge() [function.array-merge]: Argument #1 is not an array in C:\xampp\htdocs\Drupal\includes\menu.inc on line 415.
* warning: Missing argument 1 for drupal_get_form() in C:\xampp\htdocs\Drupal\includes\form.inc on line 48.
* warning: Missing argument 1 for drupal_retrieve_form() in C:\xampp\htdocs\Drupal\includes\form.inc on line 178.
* warning: call_user_func_array() [function.call-user-func-array]: First argument is expected to be a valid callback, '' was given in C:\xampp\htdocs\Drupal\includes\form.inc on line 217.